Field of the Invention
The present invention relates to an image forming apparatus such as a copier and a printer.
Description of the Related Art
Electrophotographic image forming apparatuses such as printers and copiers in which users replace components such as toner cartridges by opening/closing covers have been known, and various systems have been employed as locking mechanisms for the covers. For example, Japanese Patent Application Laid-open No. 2004-138775 discloses a configuration in which a user operates a handle to switch the position of a locking claw between a locking position and an unlocking position.
However, such a configuration in which a user operates the locking/unlocking position of a cover by a lever is not excellent in usability since it is difficult to determine a handle position or the user is not necessarily allowed to intuitively recognize an operating direction and an opening/closing direction. Therefore, as a locking mechanism for a cover to improve usability, a toggle mechanism may be used in which a user is allowed to automatically perform a drawing operation and a locking/unlocking operation, without operating a handle, as he/she opens and closes the cover.
In such a toggle mechanism, however, there is a neutral point at which an urging force is balanced in the midstream of a track along which a toggle lever rotates, and there is a point at which engagement looseness is rapidly eliminated before and after the lever has passed through the neutral point. At this time, an impact sound is generated when the toggle lever and a locked member on the side of a cover collide with each other or when a stopper member that holds the toggle lever at a standby position and the toggle lever collide with each other as the cover is opened. A description will be given, with reference to FIGS. 18A and 18B and FIGS. 19A and 19B, of a toggle mechanism.
FIG. 18A is a schematic cross-sectional view showing the configuration of a toggle mechanism and shows a state in which a toggle lever 114 is positioned at a neutral point. The toggle lever 114 is supported on a swing shaft 110 so as to be swingable about the swing shaft 110 with respect to a toggle holder 104. The toggle spring 113 is an expansion coil spring and has one end thereof attached to the toggle holder 104 and the other end thereof attached to the toggle lever 114. The toggle spring 113 continuously applies an urging force in a rotating direction to the toggle lever 114 while changing its urging force direction C as the toggle lever 114 swings. An engagement member 103 of a cover (not shown) is integrally formed with a toggle pressing region 108. When the engagement member 103 enters along a track indicated by an arrow F, the toggle lever 114 starts rotating in an arrow G direction. As shown in FIG. 18A, in a phase in which the toggle spring 113 applies the urging force to the toggle lever 114 in a direction toward the center of the swing shaft 110, the urging force of the toggle spring 113 is not converted into the rotating force of the toggle lever 114. That is, in this state, the toggle lever 114 is positioned at the neutral point. At this time, engagement looseness H exists between the toggle lever 114 and the engagement member 103, which represents looseness required for the components to reliably perform a swing operation without interference therebetween.
FIG. 18B is a schematic cross-sectional view showing the configuration of the toggle mechanism and shows a state in which the toggle lever 114 has passed through the neutral point and engages the engagement member 103 whereby the cover is locked to an apparatus main body. The engagement looseness H between the toggle lever 114 and the engagement member 103 is rapidly eliminated by the rotation of the toggle lever 114 and moves to the side of the toggle pressing region 108. At the same time, the toggle lever 114 comes in contact with the engagement member 103 by the urging force of the toggle spring 113 and completes its locking operation while urging the engagement member 103 in an arrow K direction. At this time, an impact sound is generated by an impact caused when the toggle lever 114 and the engagement member 103 collide with each other.
FIG. 19A is a schematic cross-sectional view showing the configuration of the toggle mechanism and shows a state immediately after the toggle lever 114 has passed through the neutral point when the cover is opened from its locked state. When the cover is opened from the locked state, the toggle lever 114 swings in an arrow J direction while receiving an urging force from the engagement member 103. After having passed through the neutral point as shown in FIG. 19A, the toggle lever 114 rotates in an arrow M direction by the urging force of the toggle spring 113. At this time, a gap L exists between the toggle lever 114 and a stopper region 105 that holds the toggle lever 114 at a standby position.
FIG. 19B is a schematic cross-sectional view showing the configuration of the toggle mechanism and shows a state in which the cover is opened and the toggle lever 114 is held at the standby position. The toggle lever 114 having passed through the neutral point rotates in the arrow M direction by the urging force of the toggle spring 113, the gap L between the toggle lever 114 and the stopper region 105 is rapidly eliminated, whereby the toggle lever 114 and the stopper region 105 come in contact with each other. By a collision at the contact, an impact sound is generated.
As described above, while being effective in terms of improving usability, the toggle mechanism does cause deterioration in an operation sound. In recent years, since some laser beam printers perform the pop-up operation of a toner cartridge in conjunction with a cover or hold one side of a sheet path with a jam processing cover to improve jam processing, there is a likelihood that a force required to perform the opening/closing operation of the cover increases. When a toggle mechanism is employed in the opening/closing mechanism of such an apparatus, the drawing force of a toggle lever is required to increase, which may result in deterioration in an impact sound. As means for reducing this impact sound, it is assumed to provide a buffer material such as moltopren on a collision region. However, a buffer material such as moltopren suffers from a problem in which creep deformation occurs when the buffer material receives the urging force of a toggle lever for a long period of time and the effect of the buffer material reduces.